hey ian..................congrats on ur new thread!
a few things:
both ur left gearbox mount and rear engine mounts require alot more beefing up. the GB mount is going to twist as that metal isn't thick enough.
it is likely that the rear mount is going to rotate about the point where its bolted up, you need to add a spar from this mount to the engine near to the oil filter to spread the weight more evenly.
also the rear of the subframe is missing alot of material, this needs to be plated as the 1 inch wide remaining 'joint' will break when you first drive hard and ur camber will be shot. i encourage you to look at other parts of your frame that need additional gussets and further reinforcement as well, its the little things in the final stages that makes/breaks the whole job...............
congrats again ian, it wont be long now